Chanting, “Give the heroes a raise,” more than 15,000 off-duty city cops and firefighters descended on Times Square yesterday to demand better pay in the wake of sacrifices their colleagues made on 9/11.

A sea of New York’s Bravest and Finest screamed their lungs out during the “Rally for Heroes,” in which NYPD and FDNY officials, along with several politicians and celebrities – including “Sopranos” star James Gandolfini – pressured the city to loosen its purse strings.

They also waved placards, one of which said, “They say, ‘Never forget.’ We say, ‘Already forgotten.'”

Another said, “If 23 politicians died on 9/11, you can bet they would have voted themselves a raise!” a reference to the 23 NYPD cops killed in the collapse of the Twin Towers.

“All of these politicians were at Ground Zero talking about how much we were worth,” said Brooklyn firefighter Kevin Roth. “Eleven months later, it’s business as usual. How many more guys have to die?”

Police are outraged over reports that they’ll receive a 14.1 percent pay raise under a contract arbiter’s proposal that would include 10 extra days of work per year.

Under the decision, cops will get a retroactive 5 percent increase for each of the last two years.

The Patrolmen’s Benevolent Association wants a 23 percent pay hike over two years.

Firefighters threw cold water on a pay-raise offer last August of about 4 percent a year.

“This proud Police Department and Fire Department are on the verge of death – death from a broken heart, a heart that cried on Sept. 11,” PBA President Patrick Lynch told the crowd.

Gandolfini, who plays mob boss Tony Soprano on the hit HBO series, said the city would be wise to give New York’s Finest and Bravest a hefty raise.

“The starting salary [for city cops and firefighters] is not acceptable,” he said from a stage set up at 42nd Street and Broadway. “They deserve more.”

The starting salary for a police officer is $31,000; it’s almost $33,000 for a probationary firefighter.

Sen. Hillary Rodham Clinton was both cheered and jeered by the sweltering throng.

Stephen Cassidy, president of the firefighters union, had a stern message for Mayor Bloomberg: “Do the right thing for firefighters and cops.”

Bloomberg has said he would like to give the money to the Bravest and Finest, but is hamstrung by a $5 billion deficit in the city budget.

“It’s very frustrating,” said Brooklyn firefighter Kevin Canham, 44, flanked by his three young kids. “We just want what we deserve. With what we make, we’re struggling to pay our mortgages and put food on the table for our families.”

Hung Nguyen, a 35-year-old Manhattan cop, said it’s a crime that officers are so underpaid. “Show us the money,” he said.